Magic Monday Journal Club

9th December 2013

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Dark matter detection in two easy steps

by M. Pospelov, N. Weiner and I. Yavin

So. I have chosen this article mainly because I mainly like the subject and the way the authors use to present their results: very pedagogical and usually clever ideas hidden in their work. In a sense, I was not surprise it was elected paper of the week at the end of the seance today. In this paper, the auhtors propose an original way to detect multi-component dark matter, in a word by observing the monochromatic line generated by the decay of a DM state which have been excited by its passage  through the lead shield surrounding the detector (CUORE for instance). The idea is to observe the daily modulation of such signals due to the asymmetry of the detector. They even propose to «asymmetrized» more strongly some existing ones (see their Fig.7). For the guys in a hurry before taking their train, metro, plane of rocket, just a look at their Fig.1 and 2 will give you the ideas, and the Fig.11 will give you an insight of the signal that can be expcected. They treat classical BSM extensions :dipole interaction and dark Z’, see their Eq. 1 and 6.    You can find an annoted version of the paper here.

Direct measurement of Higgs Boson Fermionic Properties

by CMS collaboration

A week after the direct evidence of Higgs coupling to fermions from ATLAS, here comes a refined analysis in the Higgs-to-tau-tau channel from CMS that now shows 3.4 sigma evidence of the signal. The measured rate is in a very good agreement with the Standard Model prediction. Not a surprising result, but another small step in measuring the Higgs coupling and confirming the Standard Model.

Flavour models with Dirac and fake gluinos

by E. Dudas, M. Goodsell, L. Heurtier and P. Tziveloglou

In the context of supersymmetric models where the gauginos may have both Majorana and Dirac masses the authors investigate the general constraints from flavour- changing processes on the scalar mass matrices. They find that the chirality-flip suppression of flavour-changing effects usually invoked in the pure Dirac case holds in the mass insertion approximation but not in the general case, and fails in particular for inverted hierarchy models. They quantify the constraints in several flavour models which correlate fermion and scalar superpartner masses. They also discuss the limit of very large Majorana gaugino masses compared to the chiral adjoint and Dirac masses, where the remaining light eigenstate is the “fake” gaugino, including the consequences of suppressed couplings to quarks beyond flavour constraints.

Constraints on Self Interacting Dark Matter from IceCube Results

by I. Albuquerque, C. P. de los Heros and D. Robertson

Knowing Carlos de los Heros, he is an experimentalist very curious and interested in phenomenology and model building. I use to meet him often especially in the annual ANTARES meeting where we discuss a lot. In this paper, he and his collaborators compute the limit on self interacting particles from the neutrinos emitted by its annihilation in the sun. Where does the self interaction enters in the game? Through the capture rate. Indeed, if a dark matter self interact, the presence of dark matter in the sun, captured by the sun itself, will enhance the capture rate (dark matter capturing itself). Physicaly speaking, the energy loss in the self-interaction will reduce the kinetic energy and thus the velocity of dark matter below the escape velocity of the sun. Jump on Eq. (2.1) and on Figure 5 if you are in a hurry: the white band is the one allowed (too large self interaction is forbidden by bullet cluster observation, too low does not reproduce the rotation curves of dwarf galaxies).  The main complaint of the attendance was concerning the existence of microscoping models when treating cross sections as large as 10^14 pb!!!! You can find an annoted version of the paper here.

Inclusive search for a vector-like T quark with charge 2/3 in pp collisions at sqrt(s)=8 TeV

by CMS collaboration

A very nice write up of the T' search results in CMS. In models addressing the hierarchy problem, such as the Little Higgs or the Composite Higgs, the heavy fermionic partner of the top quark can decay as T' -> W b, T'->Zt, or T' -> h t, with the branching fractions that are model dependent.  The new CMS analysis provides limits on the T' mass for arbitrary branching fractions into these 3 channels. The current limits are between 700 and 800 GeV. 

Doubling down on naturalness with a supersymmetric twin Higgs

by N. Craig and K. Howe

The paper follows up on the idea of double protection of the Higgs mass: via supersymmetry and pseudo-Goldstone boson mechanism at the same time.  Double protection is like wearing 2 condoms: it is very awkward, and the effect is not really worth the trouble.

The Dark Z’ and Charged Higgs decay

by R. Ramos and M. Sher

In this paper, the authors concentrate on models where the extra U(1) symmetry generating a Z’ mass term is not only due to a singlet field but also a second Higgs doublet. In a sense, it is a kind of extended 2HDM. They called this Z’ a dark Z (Zd). As a consequence, a new annihilation channel appears for the charged Higgs : H+ -> Zd W+. They show it should be largely dominant when mH+ < mt as you can see with the values of the ratio on fig.1 (from 100 to 10000). You can find an annoted version of the paper here.

On the Relative Motion of the Earth and the Luminiferous Ether

by A. Michelson and W. Morley


We discussed also the historical article which is supposed to be the basis of the Einstein theory of relativity in 1905. In fact, Einstein never mentioned Michelson’s work in his 1905 paper (but Poincarré did it in his article 2 weeks before the Einstein’s one) and used to say he did not know their work.  The paper is easy to read and conclude in the page 341 that «from all that precedes, reasonably certain that if there be say relative motion between the earth and the luminiferous ether, it must be small». In other words, it is a little bit exagerated that Michelson and Morley prove the «non-existence» of ether. The prove that ether has no relative motion with the earth, which is incompatible with the Fresnel explication of the aberration. Their main idea was to ameliorate the precision by increasing the luminous path by the introduction of mirrors (see their figure 4). It can easily be used for first year of university when studying wavelight.